Recently, parallel resonators using microstripline structured DGS and co-planar waveguide (CPW) structured DGS have been introduced. These resonators, unlike conventional resonators, have a specific pattern such as a dumbbell-like form at the ground plane in order to construct a parallel resonator. The parallel resonator obtains capacitance characteristics through the gap of the ground plane defected in the form of dumbbell and gets inductance characteristics by changing the flow of current through the ground plane defected in the form of quadrilateral.
FIG. 1 and FIG. 2 illustrate the structure of a conventional parallel resonators having a microstripline DGS and a CPW DGS respectively.
In the parallel resonator 100 with microstripline DGS structure as shown in FIG. 1, a transmission line 102 with a characteristic impedance of 50 ohm (Ω) is installed on the substrate 101, and a DGS pattern 104 defected in the shape of a dumbbell is formed on the grounding member 103 on the bottom part of the substrate 101.
The parallel resonator 200 with CPW DGS structure, as shown in FIG. 2, comprises a transmission line 202 with a characteristic impedance of 50 ohm installed on a substrate 201, and grounding members 203 which are arranged on both sides of the transmission line 202, and each grounding member 203 has a DGS pattern 204 defected in the shape of a dumbbell respectively.
In the two types of parallel resonators described above, the resonators obtain characteristics of a parallel resonator as the flow of current 205 takes the form of the defect through the defect in the shape of a dumbbell. Describing in more detail, characteristics of a parallel resonator is achieved where the capacitance characteristics being generated in the narrow gap between the dumbbell-shaped defects and the inductance characteristics being generated by the circulating flow of the current in the wide quadrilateral shape.
The parallel resonators described above have adopted a new way of designing the resonator through the defect in the ground plane, which is different from the general way of designing the circuit of super-high frequency broadband. These resonators, however, have higher transmission loss of signals due to the current radiation in the rear direction caused by the ground plane defect, and lose the characteristics of a resonator especially at high frequencies. Also it is difficult to achieve high capacitance through the gap in the form of dumbbell owing to its structural problem.
Therefore the resonators cannot have high value of quality factor.